Thermal Resecting Loop

ABSTRACT

A thermal surgical instrument comprising a conductor having a ferromagnetic material in electrical communication with the conductor, such that passage of electrical energy through the conductor causes substantially uniform heating of the ferromagnetic material sufficient to produce a desired therapeutic tissue effect is provided. The conductor may be shaped to facilitate resection of tissue from a patient and include a support to provide increase rigidity to the loop so that the conductor better resists bending during use. The ferromagnetic material quickly heats and cools in response to a controllable power delivery source. The thermal surgical instrument can be used for substantially simultaneously resecting tissue with hemostasis.

RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 12/647,340, filed Dec. 24, 2009, which claims thebenefit of U.S. Provisional Patent Application Ser. No. 61/170,203,filed Apr. 17, 2009, U.S. Provisional Patent Application Ser. No.61/170,220, filed Apr. 17, 2009, and U.S. Provisional Patent ApplicationSer. No. 61/170,207, filed Apr. 17, 2009, which are incorporated herebyby references in their entirety. The present application also claims thebenefit of U.S. patent application Ser. No. 13/441,614, filed Apr. 6,2012, which claims the benefit of U.S. Provisional Patent ApplicationSer. No. 61/473,729, filed Apr. 8, 2011, which are incorporated herebyby references in their entirety. The present application also claims thebenefit of U.S. Provisional Application Ser. No. 61/506,464, filed onJul. 11, 2011, which is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to surgical instruments. Morespecifically, the present invention relates to thermally adjustableresecting loops used in open and minimally invasive surgical proceduresand interventional surgical and therapeutic procedures.

2. State of the Art

Surgery generally involves cutting, repairing and/or removing tissue orother materials. These applications are generally performed by cuttingtissue, fusing tissue, or tissue destruction.

Current electrosurgery modalities used for cutting, coagulating,desiccating, ablating, or fulgurating tissue, have undesirable sideeffects and drawbacks. For example, monopolar and bipolar electrosurgerymodalities generally have disadvantages relating to “beyond the tip”effects. These effects are caused by intentionally passing alternatingcurrent through tissues in contact with conducting instruments orprobes.

Monopolar surgical instruments require electric current to pass throughthe patient. A return electrode is placed on the patient, often on thepatient's thigh. Electricity is conducted from a “knife” or “loop”electrode through the tissue and returns through the return electrode.Other forms of monopolar instruments exist, such as those which use thecapacitive effect of the body to act as the return electrode or ground.

A low voltage high frequency waveform will incise, but has littlehemostatic effect. A high voltage waveform will cause adjacent tissuehemostasis and coagulation. Therefore, when hemostasis is desirable,high voltage is used. The high voltage spark frequently has deepertissue effects than the cut because the electricity must pass throughthe patient. The damage to the tissue extends away from the actual pointof coagulation. Furthermore, there are complaints of return electrodeburns. Yet, any reduction of voltage reduces the effectiveness ofhemostasis. Further, the temperature of the spark or arc cannot beprecisely controlled, which can lead to undesirable charring of targettissue.

Bipolar surgical instruments can produce tissue damage and problemssimilar to monopolar devices, such as sparking, charring, deeper tissueeffects and electric current damage away from the application of energywith varying effects due to the difference in electrical conductivity oftissue types, such as nerve, muscle, fat and bone, and into adjacenttissues of the patient. However, the current is more, but notcompletely, contained between the bipolar electrodes. These electrodesare also generally more expensive because there are at least twoprecision electrodes that must be fabricated instead of the onemonopolar electrode.

Electrocautery resistive heating elements reduce the drawbacksassociated with charring and deeper tissue damage caused by otherelectrosurgery methods. However, such devices often present othertradeoffs, such as the latency in controlling heating and cooling time,and effective power delivery. Many resistive heating elements have slowheating and cooling times, which makes it difficult for the surgeon towork through or around tissue without causing incidental damage.Additionally, tissue destruction with resistively heated tools canproduce unintended collateral tissue damage.

Tissue destruction instruments generally heat tissue to a predeterminedtemperature for a period of time to kill or ablate the tissue. In somecontrolled heating of tissues, a laser is directed to an absorptive capto reach and maintain a predetermined temperature for a predeterminedamount of time. While this provides the benefits of thermal heating, itis expensive due to the complexity and expense of laser hardware.

In another tissue destruction procedure, a microwave antenna array isinserted into the tissue. These arrays are powered by instruments thatcause microwave energy to enter and heat the tissue. While such devicesare often effective at killing or ablating the desired tissue, theyoften cause deeper tissue effects than the desired area. Additionallythe procedures can require expensive equipment.

Uses of ferrite beads and alloy mixes in ceramics have been examined asan alternative to other tissue destruction methods. When excited by themagnetic field associated with high frequency current passing through aconductor, ferrite beads and alloy mixes in ceramics can reach hightemperatures very quickly. However, one major problem with the use ofthese materials is that a large temperature differential can cause thematerial to fracture, especially when it comes into and out of contactwith liquids. In other words, if a hot ferrite surgical instrument isquenched by a cooler pool of liquid, such as blood or other body fluids,the material's corresponding temperature drops rapidly and may cause thematerial to fracture. These fractures not only cause the tool to loseits effectiveness as a heat source, because the magnetic field isdisrupted, but may require extraction of the material from the patient.Obviously, the need to extract small pieces of ferrite product from apatient is highly undesirable.

In addition, removing tissue can be complicated. Removal of tissue witha blade may require several incisions or a delicate hand withcomplicated movements. Furthermore, access to a tumor may be from anangle perpendicular to the tissue. There may be little room to maneuvera blade and its handpiece to the side. This can make resecting a pieceof tissue more difficult than simply cutting through tissue.Alternatively, lasers or bipolar forceps can be employed to produce heatto dessicate the surface of the target tissue, which can then be removedwith forceps, and then the heat applied again in order to remove thenext layer of tissue if necessary. This process can be tedious andproduce unwanted bleeding that may obscure vision, complicate thesurgery and jeopardize the well-being of the patient.

Thus, there is a need for an improved thermal surgical tool to removetissue.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improvedthermally adjustable surgical or therapeutic tool.

According to one aspect of the invention, a thermal surgical instrumentsystem is provided with an arc-shaped, looped or rounded conductorhaving one or more ferromagnetic layers disposed along a length of theconductor, and an oscillating electrical energy source for generatinguniform ferromagnetic heating at the location of the one or moreferromagnetic layers with a small heat latency. This may provide theadvantage of allowing the surgeon to resect tissue, such as tumors ortissue around tumors, while reducing or eliminating bleeding. Theinstrument may seal along the coated section of the loop as it cutsthrough the tissue. Thus, a surgeon may scoop out portions of tissuewith a hemostatic effect reducing or eliminating bleeding from theremaining tissue. The scooping motion may be made with the handpiecegenerally perpendicular to the tissue, thus enabling easier removal oftissue. Further, the same loop can be turned ninety degrees and be usedto cut like a knife, with the same hemostatic effect.

According to another aspect of the invention, a thermal surgicalinstrument may include a support to provide increase rigidity to theloop so that it better resists bending during use. The support mayinclude at least one conductive intervening layer thereon with aferromagnetic material disposed in communication with the at least oneconductive intervening layer.

According to another aspect of the invention, the support may beselected from a material with desired rigidity/flexibilitycharacteristics for the particular procedure being performed and may beconductive or non-conductive.

According to another aspect of the invention, a thermal surgicalinstrument may include a body, such as a handpiece, and a cuttingelement disposed at an angle such that the cutting element is orientedin a non-parallel position with respect to the handpiece. The angle ofthe cutting element may allow better access to tissue within confinedspaces. It may also provide a better view of the surgical site becausethe cutting element is off of the center axis of the handpiece

These and other aspects of the present invention are realized in athermally adjustable instrument as shown and described in the followingfigures and related description.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention are shown and described inreference to the numbered drawings wherein:

FIG. 1 shows a perspective view of a thermal surgical instrument systemin accordance with the principles of the present invention;

FIG. 1A shows a close-up cross-sectional view of a portion of a tip ofthe thermal surgical tool system of FIG. 1;

FIG. 1B shows a close-up cross-sectional view of a portion of anothertip according to principles of the present invention;

FIG. 1C shows a close-up cross-sectional view of a portion of anothertip according to principles of the present invention;

FIG. 1D shows a fragmented cross-sectional view of a tip having a loopgeometry;

FIG. 2 shows a perspective view of an alternate embodiment of a thermalsurgical instrument system in accordance with the present invention;

FIG. 3 shows a diagram of a thermal surgical instrument system inaccordance with the principles of the present invention;

FIG. 4A shows a thermal surgical instrument system with heat preventionterminals, heat sink, and wireless communication devices;

FIG. 4B shows a thermal surgical instrument system with impedancematching network;

FIG. 4C shows a side cross-sectional view of a portion of a thermalsurgical tool system according to principles of the present invention;

FIG. 4D shows a side cross-sectional view of a portion of a thermalsurgical tool system according to principles of the present invention;

FIG. 5 shows a close-up, side cross-sectional view of a conductor havinga single layer of ferromagnetic material disposed thereon in accordancewith one aspect of the present invention;

FIG. 6 shows a close-up, side cross-sectional view of a conductor with athermal insulator and ferromagnetic material in accordance with oneaspect of the present invention;

FIG. 7A shows a close-up view of ferromagnetic conductor surgicalinstrument tip with a loop geometry in accordance with one aspect of thepresent invention;

FIG. 7B shows a close-up view of a ferromagnetic conductor surgicalinstrument tip with a generally square geometry in accordance with oneaspect of the present invention;

FIG. 7C shows a close-up view of a ferromagnetic conductor surgicalinstrument tip with a pointed geometry;

FIG. 7D shows a close-up view of a ferromagnetic conductor surgicalinstrument tip with an asymmetrical loop geometry;

FIG. 7E shows a close-up view of a ferromagnetic conductor surgicalinstrument tip with a hook geometry in which the concave portion may beused for therapeutic effect, including cutting;

FIG. 7F shows a close up view of a ferromagnetic conductor surgicalinstrument tip with a hook geometry in which the convex portion may beused for therapeutic effect, including cutting;

FIG. 7G shows a close up view of a ferromagnetic conductor surgicalinstrument tip with an angled geometry;

FIG. 8 shows a cut-away view of a retracted snare;

FIG. 9A shows a side view of an extended snare;

FIG. 9B shows an alternate embodiment of an extended snare;

FIG. 10A shows a close-up view of a ferromagnetic conductor surgicalinstrument with a loop geometry and linear array of ferromagneticsegments;

FIG. 10B shows a close up view of a ferromagnetic conductor surgicalinstrument with an alternate hook geometry and linear array;

FIG. 11 shows a cut-away view of a retracted snare with an array offerromagnetic segments;

FIG. 12 shows a side view of an extended snare with a linear array offerromagnetic segments;

FIG. 13A shows an axial cross-sectional view of a single layerferromagnetic conductor in the ferromagnetic heating region;

FIG. 13B shows an axial cross-sectional view another ferromagneticconductor in the ferromagnetic heating region according to principles ofthe present invention;

FIG. 14 shows an alternate embodiment of a ferromagnetic conductorsurgical instrument having a ferromagnetic loop tip disposed within anendoscope;

FIG. 15 shows a thermal spectrum as related to tissue effects;

FIG. 16 shows a thermal resecting instrument and system;

FIG. 17 shows a thermal resecting instrument resecting a piece oftissue, such as a tumor;

FIG. 17 shows a side, cross-sectional view of a thermal resectinginstrument resecting a piece of tissue;

FIG. 18A shows a thermal resecting instrument with an arc or loop whichis covered with ferromagnetic material in a semi-circle;

FIG. 18B shows a thermal resecting instrument with an arc which iscovered with ferromagnetic material in nearly a complete circle;

FIG. 18C shows a side view of a thermal resecting instrument with acutting element disposed at an angle such that the cutting element isoriented in a non-parallel position with respect to the handpiece; and

FIG. 18D shows an oblong thermal resecting instrument.

It will be appreciated that the drawings are illustrative and notlimiting of the scope of the invention which is defined by the appendedclaims. The embodiments shown accomplish various aspects and objects ofthe invention. It is appreciated that it is not possible to clearly showeach element and aspect of the invention in a single figure, and assuch, multiple figures are presented to separately illustrate thevarious details of the invention in greater clarity. Similarly, notevery embodiment need accomplish all advantages of the presentinvention.

DETAILED DESCRIPTION

The invention and accompanying drawings will now be discussed inreference to the numerals provided therein so as to enable one skilledin the art to practice the present invention. The drawings anddescriptions are exemplary of various aspects of the invention and arenot intended to narrow the scope of the appended claims.

As used herein, the term “ferromagnetic,” “ferromagnet,” and“ferromagnetism” refers to any ferromagnetic-like material that iscapable of producing heat via magnetic induction, including, but notlimited to, ferromagnets and ferrimagnets. It is not intended that suchmaterials must be heated exclusively by magnetic induction unlessotherwise indicated and such may acquire heat from resistive heating,eddy currents, etc., in addition to magnetic induction. The term“ferromagnetic conductor” refers to a conductor having one or morelayers of ferromagnetic material disposed in electrical communicationwith the conductor, such that passage of electrical energy through theconductor causes substantially uniform heating of the ferromagneticmaterial sufficient to produce a desired therapeutic tissue effect.

Turning now to FIG. 1, there is shown a perspective view of a thermalsurgical instrument system, generally indicated at 10. As will bediscussed in additional detail below, the thermal instrument systempreferably uses a ferromagnetic coated conductor to treat or destroytissue (e.g. endothelial tissue welding, homeostasis, ablation, etc).

It will be appreciated that the thermal surgical instrument uses heat toincise tissue and does not cut tissue in the sense of a sharp edge beingdrawn across the tissue as with a conventional scalpel. While theembodiments of the present invention could be made with a relativelysharp edge so as to form a cutting blade, such is not necessary as theheated element discussed herein will separate tissue without the needfor a cutting blade or sharp edge. However, for convenience, the termcutting is used when discussing separating tissue.

In thermal surgical instrument system 10, a control mechanism, such as afoot pedal 20 is used to control output energy produced by a powersubsystem 30. The energy from the power subsystem 30 may be sent viaradio frequency (RF) or oscillating electrical energy along a cable 40to a handheld surgical instrument 50 comprising a surgical tip 61 havinga conductor 66 with a section thereof in electrical communication with aferromagnetic material 65. For example, the conductor 66 may becircumferentially coated with a ferromagnetic material 65. Theferromagnetic material 65 may convert the electrical energy intoavailable thermal energy via ferromagnetic heating. Ferromagneticheating is uniform along the entire section of the ferromagneticmaterial 65 disposed on the electrical conductor 66, such as aconductive wire 60 shown in FIG. 1. (Conductor wire may be used hereinfor ease of reference, however, it will be appreciated that theconductor material need not be a wire and those skilled in the art willbe familiar with multiple conductors which will work in light of thedisclosure of the present invention).

Application of a magnetic field (or magnetizing) to the ferromagneticcoating may produce an open loop B-H curve (also known as an openhysteresis loop), resulting in hysteresis losses and the resultantthermal energy. Electrodeposited films, such as a nickel-iron coatinglike PERMALLOY™, may form an array of randomly aligned microcrystals,resulting in randomly aligned domains, which together may have an openloop hysteresis curve when a high frequency current is passed throughthe conductor.

The RF energy may travel along the conductor's surface in a manner knownas the “skin effect”. The current density is generally greatest at thesurface and decreases in magnitude further into the material where theelectric field approaches zero. The depth at which the skin effectcurrent is reduced to about 37 percent of its surface value is referredto as the skin depth and is a function of the electrical resistivity,the magnetic permeability of the material conducting the current, andthe frequency of the applied alternating RF current. The alternating RFcurrent in the conductor's surface induces generally uniform heating atthe location of the ferromagnetic coating.

The alternating RF current in the conductor's surface produces analternating magnetic field, which may excite the domains in theferromagnetic portion 65. As the domains realign with each oscillationof the current, hysteresis losses in the coating may cause inductiveheating. Heating of the ferromagnetic portion 65 due to hysteresis lossceases above its Curie point because the material loses its magneticproperties. Additionally, because the relative permeability of theferromagnetic portion 65 changes in response to temperature, theassociated skin depth also changes, and therefore the amount of currentconduction through the skin layer undergoes a transition near the Curiepoint. Thus, heating of the ferromagnetic portion 65 due to resistiveheating may also be reduced as it approaches the Curie point.

The ferromagnetic material 65 may have a Curie temperature. A Curietemperature is the temperature at which the material becomesparamagnetic, such that the magnetic properties of the coating are lost.When the material becomes paramagnetic, the ferromagnetic heating may besignificantly reduced or even cease. Theoretically, this should causethe temperature of the ferromagnetic material 65 to stabilize around theCurie temperature if sufficient power is provided to reach the Curietemperature. However, it has been found that the temperature of theferromagnetic material 65 may exceed its calculated Curie temperatureunder certain operational conditions. It has been observed that ifsufficient power has been applied, the tip temperature can continue torise due to resistive heating in the overall conductor and the tip canpotentially exceed the Curie temperature. When this occurs, an increasein current is observed while operating at a constant power level. It isbelieved that this may be due, at least in part to an increase in theskin depth and a resulting drop in impedance above the Curietemperature. The increase may also be due to the resistance of theferromagnetic coating dropping which in turn raises the current levelfor a fixed power level. The increased current may then cause moreresistive heating in the non-ferromagnetic portion of the conductor.Thus, it may be preferable to have a high conductivity in the conductor.

The RF conductor from the signal source up to and including the tip, mayform a resonant circuit at a specific frequency (also known as a tunedcircuit). Changes in the tip “detune” the circuit. Thus, should theferromagnetic coating 65 or the conductor 66 become damaged, the circuitmay likely become detuned. This detuning should reduce the efficiency ofthe heating of the ferromagnetic material 65 such that the temperaturewill be substantially reduced. The reduced temperature should ensurelittle or no tissue damage after breakage.

It should be understood that the handheld surgical instrument 50 mayinclude indicia of the power being applied and may even include amechanism for controlling the power. Thus, for example, a series oflights 52 could be used to indicate power level, or the handheldsurgical instrument 50 could include a switch, rotary dial, set ofbuttons, touchpad or slide 54 that communicates with the power source 30to regulate power and thereby affect the temperature at theferromagnetic material 65 to have varying effects on tissue. While thecontrols are shown on the foot pedal 20 or the handheld surgicalinstrument 50, they may also be included in the power subsystem 30 oreven a separate control instrument. Safety features such as a button ortouchpad that must be contacted to power the handheld surgicalinstrument 50 may be employed, and may include a dead man's switch.

The thermal surgical instrument system 10 allows the power output to beadjustable in order to adjust the temperature of the instrument and itseffect on tissue. This adjustability gives the surgeon precise controlover the effects that may be achieved by the handheld surgicalinstrument 50. Tissue effects such as cutting, hemostasis, tissuewelding, tissue vaporization and tissue carbonization occur at differenttemperatures. By using the foot pedal 20 (or some other user control,such as a dial 32 on the power subsystem 30) to adjust the power output,the surgeon (or other physician, etc.) can adjust the power delivered tothe ferromagnetic coating 65 and consequently control the tissue effectsto achieve a desired result. The foot pedal 20 may also be configuredonly to provide on and off, with the dial controlling power level.

Thermal power delivery can be controlled by varying the amplitude,frequency or duty cycle of the alternating current waveform, oralteration of the circuit to affect the standing wave driving theferromagnetic coated conductor, which may be achieved by input receivedby the foot pedal 20, the power subsystem 30, or the controls on thehandheld surgical instrument 50.

One additional advantage achieved by ferromagnetic heating is that theferromagnetic material can be heated to a cutting temperature rapidly.In some instances the ferromagnetic material 65 can be heated in a smallfraction of a second (e.g. as short as one quarter of a second).Additionally, because of the relatively low mass of the coating, thesmall thermal mass of the conductor, and the localization of the heatingto a small region due to construction of the handheld surgicalinstrument 50, the material may also cool extremely rapidly (e.g. insome instances approximately one half of a second). This provides asurgeon with a precise thermal instrument while reducing accidentaltissue damage caused by touching tissue when the thermal instrument isnot activated.

It will be appreciated that the time period required to heat and coolthe handheld surgical instrument 50 will depend, in part, on therelative dimensions of the conductor 66 and the ferromagnetic material65 and the heat capacity of the structure of the surgical instrument.For example, the above time periods for heating and cooling of thehandheld surgical instrument 50 may be achieved with a tungstenconductor having a diameter of about 0.375 mm and a ferromagneticcoating of a Nickel Iron alloy (such as NIRON™ available from Enthone,Inc. of West Haven, Conn.) about the tungsten conductor about 0.0375 mmthick and two centimeters long.

One advantage of the present invention is that a sharp edge is notneeded. When power is not being supplied to the surgical instrument, theinstrument will not inadvertently cut tissue of the patient or of thesurgeon if it is dropped or mishandled. If power is not being suppliedto the conductor 66 to cause heating of the ferromagnetic material 65,the “cutting” portion of the instrument quickly cools and may be touchedwithout risk of injury. This is in sharp contrast to a cutting bladewhich may injure the patient or the surgeon if mishandled. Anotheradvantage of the present invention is that the ferromagnetic heatingalong the coated section of the conductor is generally uniform andcapable of producing a uniform hemostatic effect along the entiresection of ferromagnetic material 65 in contact with tissue.

Additions may be placed on the handpiece in various locations. These mayinclude a sensor stem 12 including a sensor to report temperature or alight to illuminate the surgical area.

Turning now to FIG. 1A, there is shown a cross-sectional view of aportion of a surgical tip having a conductor 66, such as a conductorwire, in accordance with one aspect of the invention. It may bedesirable that the conductor 66 has a relatively small diameter orcross-section so as to make precise cuts in tissue, or other materials.However, it is also desirable to have the conductor 66 be relativelystiff and resist bending when encountering tissue, such as whenresecting a tumor or other tissue. To accomplish these ends, theconductor 66, as shown in FIG. 1, may be comprised of a material with aYoung's Modulus sufficient to resist bending during use and/or theconductor 66 may include a support 70, as shown in FIG. 1A, which willresist bending even when the support has a fairly small diameter orcross-section. Examples of metals having this property may includetungsten, titanium, stainless steel, Haynes 188, Haynes 25, etc.

In addition to the Young's Modulus of the support 70, other propertiesof the material used for the support 70 may be important. Theseproperties may include the resistivity of the material, the thermal andelectrical conductivity of the material, the material's heat capacity,the material's coefficient of thermal expansion, the annealingtemperature of the material, and the ability to plate a second materialto the material comprising the support 70.

In choosing a material to use as the support 70, it may be importantthat such material have the greatest amount of resistance to bendingwhile having low resistivity to minimize heating of the conductor 66 dueto resistance heating. Additionally, it may also be important that thematerial have a low heat capacity so that heat is not stored in theconductor 66 thus allowing the surgical tip to cool rapidly when notbeing used. This may help limit or prevent collateral damage tostructures adjacent the surgical site.

Additionally, it is desirable that the support 70 be comprised ofmaterial having a sufficiently high annealing temperature. At times, thesurgical tip may be operated at temperatures, for example, between about400 and 600 degrees Celsius. Thus, to avoid alterations in theproperties of the support 70, the annealing temperature of the materialused as the support 70 should be sufficiently higher than the expectedoperating ranges of the surgical tip.

Furthermore, it may be desirable that the support 70 be comprised of amaterial having a coefficient of thermal expansion value that is closeto the coefficient of thermal expansion of the ferromagnetic material65, such as a ferromagnetic coating 78, to facilitate plating of theferromagnetic coating 78 to the support 70 in some configurations.

It has been observed, however, that some materials having adequateresistance to bending (Young's modulus) during normal operation of thesurgical tip may have a coefficient of thermal expansion that is too lowfor adequate plating integrity. Thus, one or more intervening layershaving an intermediate coefficient of thermal expansion may be plated onthe conductor 66 (FIG. 1) or the support 70 and then the ferromagneticlayer 65 plated on the one or more intervening layers to provide for atransition to accommodate the difference between the coefficients ofthermal expansion of the support 70 and the ferromagnetic material 65,as described in more detail below.

Another important factor regarding the material used for the support 70is its ability to conduct electricity. There are multiple materialswhich provide adequate support, but which are not sufficientlyconductive. Thus a conductor 66 may be comprised of multiple layers ofdifferent material so as to minimize any undesirable property orproperties of the support 70.

For example, the support 70 may be conductive or non-conductive, and mayhave a one or more conductive intervening layers 74 disposed thereon,such as copper, silver, etc. or other conductive material. Theintervening layer allows the energy to pass without significantresistive heating, thus allowing the tip to cool down more rapidly. (Itwill be appreciated that the cross-sectional view of FIG. 1A is notnecessarily to scale and the support may be much larger in diameter thanthe thickness of the other layers discussed herein. Moreover, it will beappreciated that the conductive intervening layer 74 may extend theentire length of the conductor 66 as will be discussed in more detailbelow).

The material or substrate used as the support 70 may have an optimalthermal conductivity to allow for conductive cooling of the surgical tipwhen energy is not being delivered to the conductor 66. Furthermore, thesupport 70 will have a sufficiently high Young's modulus to resistbending when the surgical tool is being used to provide a thermaltherapeutic effect to tissue during a procedure. For example, thesupport 70 may be comprised of a material having a Young's Modulus(modulus of elasticity) of greater than 17 psi (118 GPa). According toone aspect of the invention, the support 70 may be comprised of amaterial having a Young's Modulus of about 58 psi (400 GPa) or greater,such as tungsten.

Furthermore, it is desirable that the intervening layer 74 be readilyattachable to the support 70. This may be accomplished by using asubstrate as the support 70 that allows for electroplating of theintervening layer 74 thereto under reasonable commercial standards. Forexample, the substrate may be easily deoxidized (“activated”) tofacilitate plating of the intervening layer 74 to the support 70.

The one or more conductive intervening layers 74 may comprise a varietyof materials, such as copper, silver, etc., having desired properties.The intervening layer 74 may be disposed along a portion of the supportor substantially extend along the entire length of the support 70. Animportant property of the intervening layer 74 is that it be a goodelectrical conductor having low resistivity such that heating due to theresistance of the intervening layer 74 is minimized. Furthermore, it isdesirable in some configurations that one of the intervening layer(s) 74not only be readily attachable to the support 70, but also be a goodsubstrate for attaching the ferromagnetic material 65, such as aferromagnetic layer or coating 78 thereto. Like the support 70, this maybe accomplish by using a substrate as the intervening layer 74 thatallows for electroplating of a ferromagnetic coating 78 thereto underreasonable commercial standards, such as a substrate that is easilyactivated to facilitate plating of the ferromagnetic layer 78.

Another important property of the intervening layer 74 in someconfigurations may be malleability. If the coefficient of thermalexpansion of the intervening layer 74 differs significantly from thecoefficient of thermal expansion of the support 70, the interveninglayer 74 may have to be sufficiently malleable so that the integrity ofthe intervening layer 74 is not easily compromised when subjected to thethermal conditions under which the surgical tip is operated. Forexample, a surgical tip including an intervening layer 74 comprised ofcopper having a linear coefficient of thermal expansion of approximately17 μm/° C. attached to a support 70 comprised of tungsten having alinear coefficient of thermal expansion of approximate 4.5 μm/° C. maybe sufficient to withstand the heat variability that the surgical tipundergoes under normal operation.

The conductor 66 of FIG. 1 also shows a ferromagnetic layer 65 disposedadjacent to the intervening layer 74. As discussed above, theferromagnetic layer 65 may be plated on the intervening layer 74. Theferromagnetic material 65 may be located along a portion of theconductor 66 at a defined location (or locations) so as to provide forlocalized heating along the surgical tip only in an area where heatingis desired. For example, the ferromagnetic layer or coating 78 may belocated along less than about 90%, 50%, 10%, etc. of the length of theconductor 66 so as to provide localized heating in a desired area. Inother words, the length which the ferromagnetic material extends may beless than the length of the conductor 66. The ferromagnetic coating 78may have high permeability to facilitate inductive or otherferromagnetic heating of the ferromagnetic material, such as NIRON™,PERMALLOY™, Co, CrO₂, etc. Additionally, the ferromagnetic coating 78may have a relatively high thermal conductance and low heat capacity tofacilitate rapid heating and cooling of the surgical tip.

According to one aspect of the invention the surgical tip may include aferromagnetic material 65 having a coefficient of thermal expansion thatvaries significantly from the coefficient of thermal expansion of thesupport 70. Such a surgical tip may also include at least oneintervening layer 74 having a coefficient of thermal expansion with anintermediate value to accommodate the differences in the coefficient ofthermal expansions of the ferromagnetic layer 65 and the support 70.Such a configuration may help maintain the integrity of the surgical tipunder expected operating conditions.

The ferromagnetic layer 65 may be exposed or may be covered with anexterior coating 80 made from a biocompatible material to ensure thatthere is no reaction between the ferromagnetic layer 65 and the patienttissues. The exterior coating 80 may also act as a lubricant between thesurgical tip and tissue which is being treated by reducing theattachment of biologic tissues to the surgical tip. For example, theexterior coating 80 may be titanium nitride (or one of its variants),TEFLON or a host of other biocompatible materials.

The exterior layer 80 may also act as an oxygen barrier to preventoxidation of the layer of ferromagnetic material 65, any interveninglayer 74, and/or the support 70. For example, it has been observed thatoxidation of the support 70 may cause the support 70 to become brittlemaking the support 70 more susceptible to damage. It will be appreciatedthat the exterior layer 80 may be disposed on the conductor 66 so as tosubstantially cover the ferromagnetic layer 65 and the entire conductor66. Alternatively, the exterior layer may be disposed on the conductor66 so as to cover the ferromagnetic layer 65 and only a portion of theconductor 66.

According to one aspect of the invention, a conductor 66 (such as theone shown in FIG. 1A) may comprise a support 70 having a diameter ofabout 500-750 μm, an intervening layer 74 having a cross-sectionalthickness of about 20-50 μm (or about 2-5 skin depths), and aferromagnetic material 65 (e.g. a coating 78) having a cross-sectionalthickness of about 2-10 μm. The thickness of the ferromagnetic material65 forming the coating 78 may be selected as a function of the skindepths of the intervening layer 74, or the combined skin depths ofmultiple intervening layers if such are included in a surgical tip asdescribed below. The antioxidation layer may be very thin, such as 1-3μm.

Turning now to FIG. 1B, there is shown a close-up cross-sectional viewof a portion of another surgical tip according to principles of thepresent invention. The tip in FIG. 1B is similar to the tip in FIG. 1Awith the addition of a second intervening layer 76. The secondintervening layer 76 may be a strike layer, such as nickel strike orgold flash, for facilitating plating of the first intervening layer 74to the support. The second intervening layer 76 may be relatively thin,for example, about 1-2 μm. The second intervening layer 76 may providefor better attachment or bonding of the first intervening layer 74 tothe support 70.

The second intervening layer 76 may have a coefficient of thermalexpansion which provides a transition to accommodate any differences inthe coefficient of thermal expansions between the support 70 and theferromagnetic material 65 (typically a ferromagnetic coating 78), andany other intervening layers, such as the first intervening layer 74. Itwill be appreciated that taking into account the coefficients of thermalexpansion of the different layers which may be used in constructing asurgical tip of the present invention to increase the durability of thesurgical tip. It will also be appreciated that additional interveninglayers, other than those shown, may be included to further provide for amore gradual transition of coefficients of thermal expansion betweenlayers. For example, the conductor 66 may include a strike layer inaddition to multiple intervening layers.

Turning now to FIG. 1C, there is shown a close-up cross-sectional viewof a portion of another surgical tip according to principles of thepresent invention. The surgical tip may comprise a conductor 66 having asupport 70 that is tubular. Thus, in the cross-sectional view the wall70 a which circumscribes a void 70 b of the support 70 can be seen. Byusing a tubular support 70 the amount of material comprising the support70 is reduced. Thus, the heat capacity of the tubular support 70 will bereduced allowing the surgical tip to cool more rapidly. While theconductor 66 is shown as being generally linear, it will be appreciatedthat the conductor can be formed into a variety of shapes.

FIG. 1D shows a fragmented cross-sectional view of a portion of asurgical tip having loop geometry. As with the surgical tips shown inFIGS. 1A-1C, the surgical tip in FIG. 1D may include a conductor 66having one or more intervening layers, a ferromagnetic material, and abiocompatible layer disposed thereon. (For ease of illustration themultiple layers are shown disposed on one side of the support 70, but itwill be appreciated that one or more of the multiple layers shown may becircumferentially disposed on the support 70). The various layers whichmake up the surgical tip may be disposed on and extend along the support70 at various lengths. For example, the second intervening layer 76 maysubstantially extend the entire length of the support 70. Likewise, thefirst intervening layer 74 (and/or any additional intervening layers)and a biocompatible layer 80 may substantially extend along the entirelength of the support 70. In the alternative, the first interveninglayer 74 and the biocompatible layer 80 may extend a short distancebeyond the ferromagnetic material 65.

As discussed above, the ferromagnetic material 65 may be disposed alongonly a portion of the conductor 66 at a defined location (or locations)so as to provide for localized heating along the surgical tip only in anarea(s) where heating is desired. As described in more detail below,different tips may be constructed having ferromagnetic material 65 whichextend different lengths along a conductor 66 extending exteriorly froma surgical handpiece. Thus, one tip may have a ferromagnetic material 65which extends only along the distal end of the exterior portion of theconductor 66, whereas another tip may have a ferromagnetic material 65which extends substantially the entire length of the exterior portion ofthe conductor 66. Additionally, the exterior portion of the conductor 66may be constructed in a variety of shapes wherein the ferromagneticmaterial 65 substantially conforms to the shape of the conductor 66.

Turning now to FIG. 2, a perspective view of another aspect of a thermalsurgical system 10 made according to principles of the present inventionis shown. In FIG. 2, the power source 30 is contained within the footpedal 20. Depending on the application and power required, theinstrument may even be entirely battery powered for relatively low powerapplications. An alternate embodiment for low power requirements mayinclude the battery, power adjustment and power delivery, allself-contained in the handle 51 of the handheld surgical instrument 50.Furthermore, a wireless communication module can be employed to send andreceive information from the handheld surgical instrument 50, includingstatus and control settings that would enable users to monitor systemperformance and alter power settings remotely from the handheld surgicalinstrument 50 itself.

It is our understanding that this thermal solution may provideadvantages over monopolar and bipolar electrical systems currentlyavailable because the thermal damage may remain very close to theferromagnetic surface of the coated region, whereas monopolar andbipolar electrical tissue ablation may frequently cause tissue damagefor a distance away from the point of contact. It is our understandingthat this method may also overcome disadvantages of other thermaldevices that rely on resistive heating which may require more time toheat and cool and thus present greater patient risk, while potentiallyhaving higher voltage requirements at the point of heating.

Furthermore, the thin ferromagnetic coating 65, which may be disposedalong a small segment of the conductor, may reduce the heating of othernon-target material in the body, such as blood when working within theheart in atrial ablation—which can lead to complications if a clot isformed. The small thermal mass of the conductor 66, and localization ofthe heating to a small region provided by the construction of theinstrument (i.e. ferromagnetic material 65 and adjacent structures)provides a reduced thermal path for heat transfer in directions awayfrom the location of the ferromagnetic material 65. This reduced thermalpath may result in the precise application of heat at only the pointdesired. As this technology alone does not employ a spark or an arc likemonopolar or bipolar technology, risks of ignition of, for example,anesthetic gasses within or around the patient are also reduced.

The thermal surgical instrument system 10 may be used for a variety oftherapeutic means—including sealing, “cutting” or separating tissue,coagulation, or vaporization of tissue. In one configuration, thethermal surgical instrument system 10 may be used like a knife orsealer, wherein the surgeon is actively “cutting” or sealing tissue bymovement of the ferromagnetic material 65 through tissue. The thermalaction of the embodiments disclosed herein may have distinct advantagesincluding substantial reduction, if not elimination, of deep tissueeffects compared with those associated with monopolar and bipolar RFenergy devices.

In another configuration, the conductor 66 having a ferromagneticmaterial 65 disposed thereon may be inserted into a lesion and set to aspecific power delivery or variable power delivery based on monitoredtemperature. The thermal effects on the lesion and surrounding tissuemay be monitored until the desired thermal effect is achieved orundesired effects are noticed. One advantage of using the conductor 66having a ferromagnetic material 65 is that it may be more cost effectivecompared to using microwave or thermal laser modalities and avoids theundesired tissue effects of microwave lesion destruction. Thus, forexample, a surgeon can contact a tumor or other tissue to be destroyedwith the ferromagnetic material 65 and precisely control treatment whilereducing or even eliminating unwanted tissue damage when the handheldsurgical instrument 50 is activated.

Sensors may be used to monitor conditions of the handheld surgicalinstrument 50 or the tissue, such as an infrared detector or sensor stem12. For instance, the temperature of the device or tissue may beimportant in performing a procedure. A sensor in the form of athermocouple, a junction of dissimilar metals, thermistor or othertemperature sensor may detect the temperature at or near theferromagnetic coating 65 or tissue. The sensor may be part of thedevice, such as a thermocouple formed as a part of the conductor or nearthe ferromagnetic coating, or separate from the handheld surgicalinstrument 50, such as a separate tip placed near the tissue orferromagnetic coating 65. The temperatures may also be correlated withtissue effects, seen in FIG. 15. Other useful conditions to monitor mayinclude, but are not limited to, color, spectral absorption, spectralreflection, temperature range, water content, proximity, tissue type,transferred heat, tissue status, impedance, resistance, voltage andvisual feedback (e.g. a camera, fiberoptic or other visualizationdevice).

The handheld surgical instrument 50 may be configured for repeatsterilization or single patient uses. More complex devices may be usefulfor repeat sterilization, while more simple devices may be more usefulfor single patient use.

A method for treating or cutting tissue may include the steps of:selecting a surgical instrument having a cutting edge and a conductordisposed adjacent the cutting edge, at least a portion of which iscoated with a ferromagnetic material; cutting tissue with the cuttingedge; and applying oscillating electrical energy to the conductor toheat the ferromagnetic material and thereby treating the cut tissue.

Optional steps of the method may include the steps of: causinghemostasis within the cut tissue; using the heated ferromagneticmaterial to incise tissue; or using the heated ferromagnetic material tocause vascular endothelial welding.

Referring now to FIG. 3, a diagram of an embodiment of the adjustablethermal surgical instrument system 10 is shown. The power delivery tothe ferromagnetic coating 65 is controlled by a modulated high frequencywaveform. The modulated waveform allows power delivery to be controlledin a manner that adjustably modifies, allows or blocks portions of thewaveform based on the desired power delivery.

In FIG. 3, an initial waveform 110 is passed through a modulator 120receiving commands from a control device, such as a foot pedal 20. Thewaveform is created by an oscillator 130 to the desired frequency andmodulated by the modulator 120, which may include, but is not limitedto, one or more of amplitude, frequency or duty cycle modulation,including a combination thereof. The resultant signal is then amplifiedby an amplifier 140. The amplified signal is sent across a tuned cable150, meaning that the cable is tuned to provide a standing wave withmaximum current and minimum voltage at the location of the ferromagneticmaterial 65 of the handheld surgical instrument 50. Alternatively, thecable 150 may not be tuned, but a circuit may be placed in the handle 51to impedance match the load of the surgical tip 61 to the power source30.

The thermal surgical instrument system 10 may be tuned by specifying thelocation of the ferromagnetic material 65 with respect to the amplifier140 (such as cable length) and tuning the high frequency signal toapproximately a resonant standing wave such that current is maximized atthe location of the ferromagnetic material 65.

It should be recognized that the surgical instrument may operate in adynamic environment. Thus when used herein, approximately a standingwave means that a circuit may be tuned such that the signal may be nearan optimal standing wave but may not achieve it, may only achieve thewave for small amounts of time, or may successfully achieve a standingwave for longer periods of time. Similarly, any use of “standing wave”without the modifier of approximate should be understood to beapproximate in the context of the thermal surgical instrument of thepresent invention.

One method for achieving such current maximization is to connect theconductor 66 to a cable 150 that is an odd multiple of one-quarterwavelengths in length and connected to the output of the amplifier 140.The design of the circuit having a resonant standing wave is intended tooptimize power delivery to the ferromagnetic coating. However, in oneembodiment, the power source 30 could be positioned at the location of(or closely adjacent to) the ferromagnetic material 65, and tuning couldbe achieved with electrical components, all within a single handheld,battery-powered instrument. Alternatively, electrical componentsnecessary for impedance matching can be located at the output stage ofthe amplifier 140. Further, electrical components, such as a capacitoror inductor, can be connected in parallel or series to the ferromagneticcoated conductor 60 at the location of the connection of the conductor66 to the cable 150, in order to complete a resonant circuit.

Dynamic load issues can be caused by the interaction of the surgical tipwith various tissues. These issues may be minimized by the standingcurrent wave being maximized at the load location. Multiple differentfrequencies can be used, including frequencies from 5 megahertz to 24gigahertz, preferably between 40 MHz and 928 MHz. In some regulatedcountries it may be preferable choose frequencies in the ISM bands suchas bands with the center frequencies of 6.78 MHz, 13.56 MHz, 27.12 MHz,40.68 MHz, 433.92 MHz, 915 MHz, 2.45 GHz, 5.80 GHz, 24.125 GHz, 61.25GHz, 122.5 GHz, 245 GHz. In one embodiment, the oscillator 130 uses anISM Band frequency of 40.68 MHz, a class E amplifier 140, and a lengthof coaxial cable 150, all of which may be optimized for power deliveryto a tungsten conductor 66 with a ferromagnetic material 65 having athickness of between 0.05 micrometer and 500 micrometers disposedthereon, and preferably the ferromagnetic material having a thickness ofbetween 1 micrometer and 50 micrometers. A useful estimate may be tostart with a ferromagnetic material 65 having a thickness of about 10%of the diameter of the conductor 66, and a length of about 5 cm.However, the ferromagnetic material 65 may be disposed as far along thelength or along multiple regions of the conductor 66 if more or lessuniform ferromagnetic heating is desired. (The ferromagnetic material 65may be formed from a Nickel Iron (NiFe) alloy, such as NIRON™ fromEnthone, Inc. of West Haven, Conn., or other ferromagnetic coatings,including Co, Fe, FeOFe₂O₃, NiOFe₂O₃, CuOFe₂O₃, MgOFe₂O₃, MnBi, Ni,MnSb, MnOFe₂O₃, Y₃Fe₅O₁₂, CrO₂, MnAs, Gd, Dy, EuO, magnetite, yttriumiron garnet, aluminum, PERMALLOY™, and zinc.)

The size of the conductor, size of the ferromagnetic coating, associatedthicknesses, shape, primary geometry, composition, power supply andother attributes may be selected based on the type of procedure andsurgeon preferences. For example, a brain surgeon may desire a smallinstrument in light handheld package designed for quick applicationwithin the brain, while an orthopedic surgeon may require a largerdevice with more available power for operation on muscle.

The conductor 66 may be formed from copper, tungsten, titanium,stainless steel, platinum and other materials that may conductelectricity. Considerations for the conductor may include, but are notlimited to mechanical strength, thermal expansion, thermal conductivity,electrical conduction/resistivity, rigidity, and flexibility. It may bedesirable to form the conductor 66 of more than one material. Connectionof two dissimilar metals may form a thermocouple. If the thermocouplewere placed in the vicinity or within of the ferromagnetic material, thethermocouple provides a temperature feedback mechanism for the device.Further, some conductors may have a resistivity that correlates totemperature, which may also be used to measure temperature.

The tuning of the power source 30 may also reduce the amount of highfrequency energy radiating into the patient to near zero, as voltage islow, and ideally zero, at the location of the ferromagnetic material 65disposed on the conductor 66. This is in contrast to monopolar devices,which require a grounding pad to be applied to the patient, or bipolardevices, both of which pass current through the tissue itself. Thedisadvantages of these effects are well known in the literature.

In many of these embodiments discussed herein, the combination of cablelength, frequency, capacitance, inductance, tip geometry, etc. may alsobe used to adjust efficiency of the surgical instrument by tuning thepower source 30 to deliver maximum power to the ferromagnetic coating65, and therefore, maximum heat to the tissue. A tuned system alsoprovides for inherent safety benefits; if the conductor were to bedamaged, the system would become detuned, causing the power deliveryefficiency to drop, and may even shut down if monitored by anappropriate safety circuit.

The amount of power delivered to the patient tissue may be modified byseveral means to provide precise control of tissue effects. The powersource 30 may incorporate a modulator 120 for power delivery asdescribed above. Another embodiment uses modification of the magneticfield by altering the geometry of the conductor 66 and/or theferromagnetic coating 65 through which it passes, such as would becaused by a magnet. Placement of the magnet nearby the ferromagneticcoating 65 would similarly alter the ferromagnetic effect and therebychange the thermal effect.

While modulation has been discussed as a method to control powerdelivery, other methods may be used to control power delivery. In oneembodiment, the output power, and correspondingly the temperature of theinstrument, is controlled by tuning or detuning the drive circuitincluding elements of the surgical tip 61.

Turning now to FIG. 4A, a thermal surgical instrument system 10 withconnectors which attach to opposing first and second ends of a conductoris shown. The conductor as shown in FIG. 4A may be formed by heatprevention terminals 280, such as crimp connectors that provide thermalisolation. One or more heat sinks 282, and wireless communicationdevices 286 may also be included. The wire conductor 66 may be connectedto the handheld surgical instrument 50 by terminals 280 and/or a heatsink 282 at opposing first and second ends of the conductor. Portions ofthe conductor may extend into the handle into terminals, while theferromagnetic material 65 disposed on the conductor 66 may extend beyondthe handle. The terminals 280 may have a poor thermal conductance suchthat the terminals 280 reduce the heat transfer from the conductor 66into the handheld surgical instrument 50. In contrast, the heat sink 282may draw any residual heat from the terminals 280 and dissipate the heatinto other mediums, including the air. Connectors and connections mayalso be achieved by wire bonding, spot and other welding, in addition tocrimping.

Preventing thermal spread may be desirable because the other heatedportions of the handheld surgical instrument 50 may cause undesiredburns, even to the operator of the handheld surgical instrument 50. Inone embodiment, terminals 280 are used to conduct the electric current,but prevent or reduce thermal conduction beyond the exposed portion ofthe conductor 66.

The thermal surgical instrument may also communicate wirelessly.According to one aspect of the invention, the user interface formonitoring and adjusting power levels may be housed in a remote,wirelessly coupled device 284. The wirelessly coupled device maycommunicate with a wireless module 286 contained within the thermalsurgical instrument system 10, including the handheld surgicalinstrument 50, the control system (such as footpedal 20), and/or thepower subsystem 30. By housing the control interface and display in aseparate device, the cost of the handheld surgical instrument 50 portionmay be decreased. Similarly, the external device may be equipped withmore processing power, storage and, consequently, better control anddata analysis algorithms.

Turning now to FIG. 4B, a thermal surgical instrument system withimpedance matching network is shown. The impedance matching network maymatch the output impedance of the signal source to the input impedanceof the load. This impedance matching may aid in maximizing power andminimizing reflections from the load.

According to one aspect, the impedance matching network may be a balun281. This may aid in power transfer as the balun 281 may match theimpedance of the ferromagnetic coated conductor terminals 287 to theamplifier cable terminals 283 (shown here as a coaxial cableconnection). In such a configuration, some baluns may be able to act asa heat sink and provide thermal isolation to prevent thermal spread fromthe thermal energy at the ferromagnetic material 65 transferred by theconductor 66 to terminals 287. The appropriate matching circuitry mayalso be placed on a ceramic substrate to further sink heat away orisolate heat away from the rest of the system, depending on thecomposition of the substrate.

It should be recognized that the elements discussed in FIGS. 4A and 4Bcan be used in conjunction with any of the embodiments shown herein.

Turning now to FIG. 4C, there is shown a portion of a thermal surgicaltool system according to principles of the present invention. Thethermal surgical tool system may include a conductor 66 comprising asupport 70 and one or more intervening layers 74 (including a strikelayer 76 shown in FIG. 1B), a ferromagnetic portion 65 (typically formedby a ferromagnetic layer 78), and a biocompatible layer 80. Theconductor 66 of the thermal surgical tool system may be attached to aprinted circuit board 79. Depending on the material used as the support70, attachment of the conductor to the printed circuit board 79 may befacilitated by conductively connecting the conductor to the printedcircuit board 79 via the intervening layer 74. For example, anintervening layer 74 comprised of copper may be more readily attachableto the printed circuit board 79 than a support comprised of tungsten.Additionally, the support 70 could be attached mechanically and have anintervening layer to connect the conductor 66 to the printed circuitboard electrically.

Alternatively, a sleeve 75 may be disposed on the support 70 tofacilitate attachment of the conductor 66 to the printed circuit board79 as is shown in FIG. 4D. The sleeve 75 may be attached to the support70, for example by TIG welding the sleeve 75 to the support 70. Thesleeve 75 may be disposed on the support 70 such that the sleeve 75 isin contact with or connected to the intervening layer 74, as indicatedby location 71, so that electrical energy may be transferred from thesleeve 75 to the intervening layer 74 and thereby cause heating of theferromagnetic portion 65. Thus, in contrast to the intervening layer 74shown in FIG. 4C, the intervening layer 74 shown in FIG. 4D does notextend along the entire length of the support.

Turning now to FIG. 5, a longitudinal cross section of a conductorhaving a ferromagnetic material disposed thereon is shown. As analternating current 67 is passed through conductor 66 causing heating inthe ferromagnetic material 65. As there is very little mass to theferromagnetic material 65, the passage of alternating current causes theferromagnetic material 65 to quickly heat. Similarly, the ferromagneticcoating 65 is small in mass compared to conductor 66 and therefore heatwill quickly dissipate therefrom due to thermal transfer from the hotferromagnetic material 65 to the cooler and larger conductor 66, as wellas from the ferromagnetic material 65 to the surrounding environment.

It should be appreciated that while the figures show a solid circularcross-section, the conductor cross-section may have various geometries.For instance, the conductor may be a hollow tubing such that it reducesthermal mass. Whether solid or hollow, the conductor may also be shapedsuch that it has an oval, triangular, square or rectangularcross-section.

As is also evident from FIG. 5, the ferromagnetic coating may be betweena first section (or proximal portion) and a second section (or distalportion) of the conductor. This may provide the advantage of limitingthe active heating to an area smaller than the entire conductor. A powersupply may also connect to the first and second section to include theferromagnetic material within a circuit providing power.

A method of making the surgical instrument may include the steps of:selecting a conductor and plating a ferromagnetic material upon theconductor, such that passage of electrical energy through the conductorcauses substantially uniform ferromagnetic heating of the ferromagneticmaterial, wherein the ferromagnetic heating is sufficient to produce adesired therapeutic tissue effect.

Optional steps to the method may include: selecting a size of aconductor having a ferromagnetic material disposed on a portion thereofaccording to a desired procedure; selecting a thermal mass of aconductor having a ferromagnetic material disposed on a portion thereofaccording to a desired procedure; selecting a conductor from the groupof loop, solid loop, square, pointed, hook and angled; configuring theoscillating electrical signal to heat the ferromagnetic material tobetween 37 and 600 degrees Centigrade; configuring the oscillatingelectrical signal to heat the ferromagnetic material to between 40 and500 degrees Centigrade; causing the ferromagnetic material to heat tobetween about 58-62 degrees Centigrade to cause vascular endothelialwelding; causing the ferromagnetic material to heat to between about70-80 degrees Centigrade to promote tissue hemostasis; causing theferromagnetic material to heat to between about 80-200 degreesCentigrade to promote tissue searing and sealing; causing theferromagnetic material to heat to between about 200-400 degreesCentigrade to create tissue incisions; or causing the ferromagneticmaterial to heat to between about 400-500 degrees Centigrade to causetissue ablation and vaporization. Treatment may include incising tissue,causing hemostasis, ablating tissue, or vascular endothelial welding.

Turning now to FIG. 6, a close-up, longitudinal cross-sectional view ofa single layer cutting tip with a thermal insulator 310 is shown. Alayer of thermal insulator 310 may be placed between the ferromagneticmaterial 65 and the conductor 66. Putting a layer of thermal insulator310 may aid in the quick heating and cool-down (also known as thermalresponse time) of the instrument by reducing the thermal mass bylimiting the heat transfer to the conductor 66.

The thickness and composition of the thermal insulator may be adjustedto change the power delivery and thermal response time characteristicsto a desired application. A thicker layer of thermal insulator 310 maybetter insulate the conductor 66 from the ferromagnetic coating 65, butmay require an increased power compared with a thinner layer of thermalinsulator 310 in order to induce a magnetic field sufficient to causethe ferromagnetic material 65 to heat.

In the embodiments shown in FIGS. 7A-7G a plurality of embodiments areshown in which the surgical tip 210 includes a conductor 66 which has aportion of its length coated or in electrical communication with arelatively thin layer of ferromagnetic material 65. As shown in FIGS.7A-7G, the ferromagnetic material 65 may be a circumferential coatingaround a wire conductor 66. When the wire conductor 66 is excited by ahigh frequency oscillator, the ferromagnetic material 65 will heatthrough induction or other ferromagnetic heating according to the powerdelivered. Because of the small thickness of ferromagnetic material 65and the tuned efficiency of high frequency electrical conduction of thewire at the position of the ferromagnetic material 65, the ferromagneticmaterial 65 will heat very quickly (i.e. a small fraction of a second)when the current is directed through the wire conductor 66, and cooldown quickly (e.g. a fraction of a second) when the current is stopped.

Turning now to FIGS. 7A, 7B, 7C, 7D, 7E, 7F and 7G, surgical tipscomprising conductors with ferromagnetic layers 210 a, 210 b, 210 c, 210d, 210 e, 210 f and 210 g are shown. In each of these embodiments, aportion of the conductors 66 are bent and in electrical communicationwith a ferromagnetic material 65 such that the ferromagnetic material 65is only exposed to tissue where the desired heating is to occur. FIGS.7A and 7B are loop shapes that can be used for tissue cutting orexcision, depending upon the orientation of the instrument to thetissue. FIG. 7A shows a rounded geometry, while FIG. 7B shows a squaredgeometry. FIG. 7C shows a pointed geometry for heated tip applicationsthat can be made very small because the process of tissue dissection,ablation, and hemostasis requires only a small contact point. FIG. 7Dshows an asymmetric instrument with a loop geometry, where theferromagnetic material 65 is only disposed on one side of theinstrument. FIG. 7E shows a hook geometry where the ferromagneticmaterial 65 is disposed on the concave portion of the hook. FIG. 7Fshows a hook geometry where the ferromagnetic material 65 is disposed onthe convex portion of the hook. FIG. 7G shows an angled geometry, whichmay be used in similar situations as a scalpel. Use of these variousgeometries of ferromagnetic material 65 upon a conductor 66 may allowthe surgical tip to act very precisely when active and to be atraumaticwhen non-active.

In one representative embodiment, the electrical conductor may have adiameter of 0.01 millimeter to 1 millimeter and preferably 0.125 to 0.5millimeters. The electrical conductor may be tungsten, copper, othermetals and conductive non-metals, or a combination such as twodissimilar metals joined to also form a thermocouple for temperaturemeasurement. The electrical conductor may also be a thin layer ofconductor, such as copper, dispersed around a non-metallic rod, fiber ortube, such as glass or high-temperature plastic, and the conductivematerial, in-turn, may have a thin layer of ferromagnetic materialdisposed thereon. The magnetic film forms a closed magnetic path aroundthe electrically conductive wire or other conductor. The thin magneticfilm may have a thickness about 0.01-50% and preferably about 0.1% to20% of the cross-sectional diameter of the wire.

It is therefore possible to operate at high frequencies with lowalternating current levels to achieve rapid heating. The same minimalthermal mass allows rapid decay of heat into tissue and/or the conductorwith cessation of current. The instrument, having low thermal mass,provides a rapid means for temperature regulation across a therapeuticrange between about 37 degrees Celsius and 600 degrees Celsius, andpreferably between 40 and 500 degrees Celsius.

A material with a Curie point beyond the anticipated therapeutic needmay be selected and the temperature can be regulated below the Curiepoint.

While some tip geometries are shown in FIGS. 7A through 7G, it isanticipated that multiple different geometries may be used in surgicaltips made according to principles of the present invention.

Turning now to FIG. 8, a cut-away view of a snare 350 in a retractedposition is shown. A ferromagnetic material is placed on a conductor toform a snare loop 355 and then placed within a sheath 360. Whileretracted, the snare loop 355 may rest within a sheath 360 (or someother applicator, including a tube, ring or other geometry designed toreduce the width of the snare when retracted). The sheath 360 compressesthe snare loop 355 within its hollow body. The sheath 360 may then beinserted into a cavity where the target tissue may be present. Once thesheath 360 reaches the desired location, the snare loop 355 may beextended outside the sheath 360, and end up deployed similar to FIG. 9A.In one embodiment, the conductor 66 may pushed or pulled to causeextension and retraction of the snare loop 355.

Turning now to FIG. 9A, a side view of a snare 350 in an extendedposition is shown. Once extended, the snare loop 355 may be used inseveral different ways. In one embodiment, the snare loop 355 may beplaced substantially around the target tissue, such that the tissue iswithin the snare loop 355. The ferromagnetic coating may then be causedto be heated as discussed above. The snare loop 355 is then retractedback into the sheath 360 such that the target tissue is separated andremoved from tissue adjacent the target tissue. The desired temperaturerange or power level may be selected for hemostasis, increased tissueseparation effectiveness or other desired setting. For example, thesnare 350 may be configured for nasal cavity polyp removal.

In another use, the snare 350 may be configured for tissue destruction.Once within the desired cavity, the snare may be extended such that aportion of the snare loop 355 touches the target tissue. The snare loop355 may then be heated such that a desired tissue effect occurs. Forexample, the sheath may be placed near or in the heart and the snareloop 355 heated to cause an interruption of abnormal areas of conductionin the heart, such as in atrial ablation.

Turning now to FIG. 9B, an alternate embodiment of a snare 351 is shown.The applicator may be a ring 361 instead of a sheath as in FIG. 9A.Similar to the sheath, the ring 361 may be used to force the loop intoan elongated position. Various devices could be used to hold the ring inplace during use.

A method of separating tissue may include the steps of: selecting aconductor having a ferromagnetic material disposed on a portion thereof;placing the portion of the conductor having the ferromagnetic materialwithin a tube; inserting the tube into a cavity; deploying the portionof the conductor having the ferromagnetic material within the cavity;and delivering an oscillating electrical signal to the conductor so asto heat the ferromagnetic material while the heated ferromagneticmaterial is in contact with a target tissue.

Optional steps may include: the deploying step further comprises placingthe ferromagnetic material substantially around the target tissue;retracting the ferromagnetic material portion of the conductor into thetube; causing hemostasis in the target tissue; forming the conductorinto a bent geometry such that a portion of the conductor remains withinthe tube; and touching a ferromagnetic covered portion of the bentgeometry to the target tissue.

A method of removing tissue may include the steps of: selecting aconductor having at least one portion having a ferromagnetic conductordisposed thereon; and placing the ferromagnetic conductor around atleast a portion of the tissue and pulling the ferromagnetic conductorinto contact with the tissue so that the ferromagnetic conductor cutsthe tissue.

Optional steps may include: using a conductor having a plurality offerromagnetic conductors in an array or passing an oscillatingelectrical signal through the conductor while the ferromagnetic materialis in contact with the tissue.

Turning now to FIG. 10A, a close-up view of a cutting tip with a loopgeometry and linear array of coatings is shown. According to one aspectof the invention, there may be more than one layer of ferromagneticmaterial separated by gaps along the length of a single conductor. Thisis termed a linear array of ferromagnetic elements.

According to one aspect, a loop geometry 270 a may have multipleferromagnetic layers 65, 65′, and 65″ which are separated by gaps on aconductor 66. In another embodiment shown in FIG. 10B, a close up viewof a cutting tip with an alternate hook geometry 270 b and linear arrayof ferromagnetic coatings 65 and 65′ is shown on a conductor 66. Thelinear array may include the advantage of allowing flexibility inbuilding a desired thermal geometry.

The conductor 66 which may be formed of an alloy having shape memory,such as Nitinol (nickel titanium alloy). A Nitinol or other shape memoryalloy conductor can be bent into one shape at one temperature, and thenreturn to its original shape when heated above is transformationtemperature. Thus, a physician could deform it for a particular use at alower temperature and then use the ferromagnetic coating to heat theconductor to return it to its original configuration. For example, ashape memory alloy conductor could be used to form snare which changesshape when heated. Likewise, a serpentine shape conductor can be made ofNitinol or other shape memory alloy to have one shape during use at agiven temperature and a second shape at a higher temperature. Anotherexample would be for a conductor which would change shape when heated toexpel itself from a catheter or endoscope, and then enable retractionwhen cooled.

In another embodiment, the ferromagnetic layers may be formed in such away that an individual layer among the linear array may receive morepower by tuning the oscillating electrical energy. The tuning may beaccomplished by adjusting the frequency and/or load matching performedby the power source to specific ferromagnetic layers.

Turning now to FIG. 11, a cut-away view of a snare instrument 370 with alinear array of ferromagnetic layers in a retracted position is shown.Some ferromagnetic materials may lack the elasticity to effectively bendinto a retracted position. Therefore, individual segments 65 may beseparated by gaps 380 such that the conductor 66 may be flexed while theferromagnetic segments 66 may remain rigid.

Similarly, the snare instrument 370 may be extended, as seen in FIG. 12.The gaps 380 between the ferromagnetic segments 65 may be adjusted suchthat the heating effect will be similar in the gaps 380 as the coatingsegments. Thus, the snare instrument 370 with linear array may actsimilar to the snare with a single, flexible ferromagnetic layer shownin FIGS. 8 and 9.

Turning now to FIG. 13A, a cross-sectional view of a single layercutting tip in the ferromagnetic heating region is shown. Theferromagnetic material 65 is disposed over a conductor 66. Theferromagnetic coating 65 provides several advantages. First, theferromagnetic coating 65 is less fragile when subjected to thermalstress than ferrite beads, which have a tendency to crack when heatedand then immersed in liquid. The ferromagnetic conductor has beenobserved to survive repeated liquid immersion without damage. Further,the ferromagnetic material 65 has a quick heating and quick coolingquality. This is likely because of the small amount of ferromagneticmaterial 65 that is acted upon by the alternating current, such that thepower is concentrated over a small area. The quick cooling is likelybecause of the small amount of thermal mass that is active during theheating. Also, the composition of the ferromagnetic material 65 may bealtered to achieve a different Curie temperature, which may provide abroader thermal operating range below the Curie temperature.

The ferromagnetic material 65 can be used to contact the tissuedirectly, or, a non-stick coating, such as TEFLON (PTFE), or similarmaterial, could be applied over the ferromagnetic coating and conductorto prevent sticking to the tissue (as shown in FIG. 13B). Alternatively,the ferromagnetic material could be covered with another material, suchas gold, to improve biocompatibility, and/or polished, to reduce dragforce when drawing through tissue. The ferromagnetic material 65 couldalso be covered by a thermally-conductive material to improve heattransfer. In fact, single or multi-layered coatings beneath theferromagnetic material or on top of the ferromagnetic material may beselected to have multiple desirable properties as discussed in moredetail below.

Turning now to FIG. 13B, a cross-sectional view of a surgical tip in theferromagnetic-portion is shown. The ferromagnetic portion 65 may bedisposed circumferentially about a conductor 66. The surgical tip may beconstructed of multiple layers. Each of the multiple layers may comprisea different material, or combinations of the same or differentmaterials, so as to take advantage of the different properties of thevarious materials when used as a surgical tip. For example, theconductor 66 may include a support 70 which may be comprised of amaterial having a high Young's modulus, i.e. strength to resist bending.The conductor 66 may also include an the intervening layer 76, which maybe a strike layer to facilitate attachment of additional layers, and anintervening layer 74, which may comprise one or more layers of copper,silver, or other material which is highly conductive. The ferromagneticmaterial 65, which may be a thin layer or coating 78 is then attached tothe intervening layer 74 and a biocompatible material 80 may be disposedover substantially all or a portion of the length of the conductor 66. Amethod for tissue destruction may include the steps of selecting aconductor having a ferromagnetic material disposed on a portion thereof;and delivering an oscillating electrical signal to the conductor so asto heat the ferromagnetic material and destroy tissue.

Optional steps of the method may include monitoring the tissue andceasing delivery of the oscillating electrical signal to the conductorwhen the desired tissue destruction has occurred or undesired tissueeffects are to be prevented.

Optional steps of the method may include providing electricalconnections on the conductor configured for receiving oscillatingelectrical energy.

Turning now to FIG. 14, an endoscope 240 with a viewing channel 262 ofrod lens type or organized fiber bundle type aside a light emittingsource 266 is shown. A loop coagulator/cutter 264 is shown whichcomprises the ferromagnetic conductor 65. Such an adaptation iscontemplated in snare applications such as colon polypectomy or sealingand cutting applications in various laparoscopic procedures. Othersensing modalities include near field tumor cell detection or infraredheat monitoring. Instrument configurations similar to the describedendoscope 240 can be embodied in instruments that can be delivered totarget tissue through the lumen of a catheter.

According to one aspect, tumor cells are caused to be tagged withmaterials that fluoresce when exposed to ultra-violet light. Theendoscope 240 may contain a light source 266, and sensor or opticswithin the channel 262 that return the detected florescence. Theferromagnetic material 65 portion of the endoscope 240 may then bedirected at the tagged tissue for destruction.

According to another aspect, materials are deposited around targettissue or bone in a solidified condition. Once delivered, the materialsare melted to conformation at the site by activation by the endoscope240 described above. Examples of use of this embodiment includefallopian tube sealing and osteosynthesis. Furthermore, such materialscould be removed by melting with the same or similar endoscope 240, andaspirated through a central lumen of the endoscope 240. In yet furtherapplications, materials may be delivered in liquid form, and cured by athermal heating process induced by the endoscope 240.

Alternatively, the conductor may be part of a bundle of fibers. Thefibers may be contained within a catheter or otherwise bundled together.The conductor may have a ferromagnetic layer, while the other fibers mayhave other purposes that include visual observation, sensing,aspiration, or irrigation.

A method of tissue ablation may include the steps of: selecting acatheter with a ferromagnetic covered conductor; causing theferromagnetic covered conductor to touch tissue to be ablated; anddelivering power to the ferromagnetic covered conductor.

Optional steps may include: directing the catheter to the tissue throughthe aid of an endoscope; selecting a ferromagnetic conductor disposed onthe catheter; selecting a ferromagnetic conductor contained within thecatheter; causing the ferromagnetic conductor to be deployed from thecatheter; or touching the ferromagnetic conductor to the tissue to beablated.

A method of delivering a substance into a body may include the steps of:selecting a catheter with a ferromagnetic conductor; placing a substancein the catheter; inserting the catheter into a body; and causing powerto be sent to the ferromagnetic conductor.

Optional steps may include: selecting a substance for osteosynthesis;selecting a substance for fallopian tube sealing; or melting thesubstance in the catheter.

A method of treating tissue may include the steps of: selecting acatheter with a ferromagnetic conductor; placing the catheter in contactwith tissue; and selecting a power setting. The temperature range maycorrespond to a temperature range or desired tissue effect. The desiredtissue effect may be selected from the group of vascular endothelialwelding, hemostasis, searing, sealing, incision, ablation, orvaporization. In fact, the power setting may correspond to a desiredtissue effect.

Turning now to FIG. 15, a temperature spectrum is disclosed. Tissue mayreact differently at different temperatures with a tissue treatmentelement (such as a ferromagnetic conductor) and thus temperature rangeswill result in different treatments for tissue. Specific tissuetreatments are somewhat variable due to inconsistencies including tissuetype and patient differences. The following temperatures have been foundto be useful. Vascular endothelial welding may be optimal at 58-62degrees Centigrade. Tissue hemostasis without sticking may be achievedat 70-80 degrees Centigrade. At higher temperatures, tissue searing andsealing may occur more quickly, but coagulum may build-up on theinstrument. Tissue incision may be achieved at 200 degrees Centigradewith some drag due to tissue adhesion at the edges. Tissue ablation andvaporization may occur rapidly in the 400-500 degree Centigrade range.Thus, by controlling the temperature the “treatment” of tissue which thedevice delivers can be controlled, be it vascular endothelial welding,tissue incision, hemostasis or tissue ablation.

Besides the advantages of uses in tissue, the surgical instrument mayalso be self-cleaning. In one embodiment, when activated in air, theinstrument may achieve a temperature sufficient to carbonize or vaporizetissue debris.

According to the spectrum disclosed above, power delivery settingscorresponding to the desired temperature range may be included in thepower delivery switch. In one embodiment, the foot pedal may haveseveral stops that indicate to the surgeon the likely tip temperaturerange of the current setting.

Turning now to FIGS. 16 to 18C, a thermal resecting instrument is shown.A thermal resecting instrument may allow a surgeon to separate and scooptissue while providing the benefits of hemostasis. To this end, theconductor may be shaped to enclose or substantially enclose a voidthrough which cut tissue will pass. It will be appreciated that theshape of the conductor 66 may be arc-shaped, similar to that shown inFIG. 7A, loop shaped similar to that shown in FIGS. 9A and 9B, oblongsimilar to that shown in FIG. 8 or 25, squared or squared-off similar tothat shown in FIG. 7B, angular or pointed similar to that shown in FIG.7C or any other shape which can be used for tissue resecting. Thedrawings show the conductor as being generally loop shaped but should beconsidered to show the other shapes as well. Additionally, it will beappreciated that the ferromagnetic material may cover and extend alongthe conductor for various lengths depending on the desired use.

As mentioned with respect to FIGS. 7A and 7B, a shaped ferromagneticconductor can be used both for cutting and excising tissue. When held inone orientation, the outer surface of the shaped ferromagnetic conductorwill cut like a knife. When rotated 90 degrees or some other angle, thecutting element can cut out tissue, either by cutting off tissue (i.e. apolyp) or scooping out tissue (i.e. a tumor) without substantiallychanging the orientation of the handle.

Turning now to FIG. 16, a thermal resecting instrument 400 and system410 is shown. The thermal resecting instrument system 410 may include ahandpiece 420 and power supply 430. The power supply 430 may supplypower and receive control input from the handpiece 420.

The handpiece 420 may include an arc-shaped or loop-shaped conductor 66having a ferromagnetic layer 65 disposed about a void 454, power display460, push button control 470 and supply terminals 480 for receiving acable 490. Power directed to the conductor 66 may cause theferromagnetic layer 65 to heat. The power display may receiveinformation from the power supply 430 and display current information,such as the current power setting. Push button control 470 may sendinformation to the power supply 430, such as directing the power supplyto start supplying power or turn off power depending on the currentstate of power. The handpiece 420 may also be removably attached to thecable 490 through supply terminals 480.

The power supply 430 may include a signal generator, display 500,controls 510, handpiece terminals 520, control terminals 530 and remotecontrol functionality, such as a foot pedal 540. The signal generatormay prepare a waveform to be sent to the handpiece 420. The display 500may be used with the controls 510 to view and edit settings, includingpower level, waveform, and tip configuration. Handpiece terminals may beused to connect the handpiece 420 to the power supply through one ormore cables 490, including delivering power, suction, insufflation, etc.Control terminals 530 may allow connection of external controls, such asa foot pedal 540. The external controls may be used to alter settings,such as power level, suction power, airflow or irrigation.

In one embodiment, a surgeon may preset the device to specific settings,including power levels and waveforms. The surgeon may then select a tipor handpiece with the desired loop configuration, such as size,diameter, angle and thickness, and connect the handpiece to the powersupply 430 through handpiece terminals 520. The surgeon may control thehandpiece power levels and other options through the use of handpiececontrols, such as push button control 470 and foot pedal 540. When thedesired setting is achieved, the surgeon may scoop tissue by placing theferromagnetic coating against the tissue and pushing or pulling thehandpiece to drive the handpiece into the tissue and then out again.Optionally, a surgeon may also save frequently used settings as“favorites.”

FIGS. 17 and 17A show a thermal resecting instrument 400 resecting atumor 550. A ferromagnetic covered conductive loop 560 forming aferromagnetic region and defining a void 454 for receiving tissue, sothat the loop 560 may be used to scoop larger or smaller amounts oftissue, such as tumor 550. Larger amounts of tissue may be removed bycausing the loop 560 to enter deeper into the tissue. Smaller amounts oftissue may be removed by causing the loop 560 to enter more shallowly orby scraping the surface. In either, case, the loop 560 may resect tissuewith a single motion. In other words, the loop 560 may be disposed at anangle relative to the path of travel (indicated by arrow 558 in FIG.17A) and be advanced below a surface level of the tumor 550 or othertissue being resected (as more clearly shown in FIG. 17A) to therebyleave a three dimensional void in the tumor 550 or other tissue whilesimultaneously cauterizing the tissue so as to stop bleeding, etc. Thus,the loop 560 could scoop out a portion of tissue and thereby remove atumor 550 or other growth and seal the wound with a single passLikewise, the loop 560 can be used to remove undesirable tissue, etc.,one scoop or pass at a time with each pass leaving the tissue sealed.Such may allow a surgeon, for example, to repeatedly advance through atumor or other tissue which is desired to be removed, and then observewith each pass whether all of the undesirable tissue has been moved.

By rotating the angle of the loop 560, the surgeon can control thecross-sectional area of the three dimensional void or channel left oncethe undesirable tissue has been removed. For example, a surgeon couldrotate the loop 560 and insert the loop 550 into the tissue at a 45degree angle to the path of travel 558, for example, to cut a voidhaving a first width, and then rotate the loop to be generallyperpendicular to the zone of the travel 558 to resect a wider portion oftissue. Thus, the surgeon can adjust the position of the loop tominimize or maximize the amount of tissue at any particular locationbeing taken out with a single pass.

Contrasted with a blade (and even many electrosurgical devices), theblade may require several cuts and/or a more complex circular motion toremove tissue. Thus, the loop 560 provides the advantage of a singlemotion to resect tissue three dimensionally with the advantages ofremoving smaller or larger portions of tissue with hemostasis.

Alternatively, the loop 560 may be rotated so that an outer surface(e.g. a surface of the loop opposite the void 454) can be used to incisetissue. Thus, the loop 560 can be used as either, or both, a resectinginstrument by surrounding tissue such that the tissue is located withinthe void 454 and drawing the loop 560 through the tissue, or more like atraditional blade or scalpel to incise tissue.

Resecting tumors with the thermal resecting instrument 400 may provideseveral benefits. As some tumors promote angiogenisis (increase bloodvessel formation) they may have increased blood flow. Thus, hemostasismay become more important as the surgeon is able to cut and sealsimultaneously. As the thermal resecting instrument 400 may resecttissue while providing hemostasis on the tissue remaining, bleeding maybe reduced. Reduced bleeding may provide a clearer operating site andreduce patient blood loss.

A ferromagnetic covered conductive loop 560 may be produced in a varietyof shapes, diameters, sizes, thicknesses and other configurationsadapted to the needs of the surgeon. For example, FIGS. 18A-18D showexemplary ferromagnetic covered conductive loops having ferromagneticregions. FIG. 18A shows a thermal resecting instrument with asemi-circular ferromagnetic region; FIG. 18B shows a thermal resectinginstrument with a near circular ferromagnetic region; FIG. 18C shows aside view of a thermal resecting instrument with a cutting elementdisposed at an angle such that the cutting element is oriented in anon-parallel position with respect to the handpiece 420; and FIG. 18Dshows an oblong thermal resecting instrument.

The shape of the arc may determine the depth versus volume of tissueremoved. Comparing FIG. 18B with FIG. 18D, the rounded shape of FIG. 18Bmay remove more tissue across a greater diameter. The oblong shape of18D may allow a more targeted, but deeper removal of tissue.

The size of the conductor 66, shape of the conductor 66 and area coveredby the ferromagnetic layer 65 disposed along the conductor 66 may alsoaffect the amount of tissue removed. The semi-circular arc of FIG. 18A,may be used to remove tissue at a more shallow depth than the full arcof FIG. 18B, without the creation of excessive heat.

An angle of the cutting element, as seen fin FIG. 18C, may aid insurgery. For example, the angle of the cutting element may allow betteraccess to tissue within confined spaces. It may also provide a betterview of the surgical site because the cutting element is off of thecenter axis of the handpiece.

It will be appreciated that the thermal surgical instrument system inaccordance with the present invention will have a wide variety of uses.Not only can it be used on humans, it can also be used to cut tissue ofother animals, such as in the context of a veterinarian or simplycutting tissues or biomaterials, such as those used for implantation,into smaller pieces for other uses.

Certain embodiments of the surgical system may have broad applicationwithin surgery as well. A loop geometry may have advantages in cutting,coagulation and biopsy applications. A blade geometry may haveadvantages for cutting and hemostasis applications. The point geometrymay have advantages in dissection and coagulation applications, and inparticular, neurodissection and coagulation. However, the application ofa geometry may be further configured and tailored to an application bydiameter, length, material characteristics and other characteristicsdiscussed above.

While the present invention has been described principally in the areaof surgical instruments and the treatment of live tissue (though it canbe used on dead tissue as well), it will be understood that aninstrument made in accordance with the present invention and the methodsdiscussed herein may have other uses. For example, a cutting instrumentcould be formed for butchering meat. Whether the meat is fresh orfrozen, the instrument can be useful. For example, a cutting blade whichis heated to a high temperature will cut through frozen meat. However,when power is no longer supplied, the “cutting” edge is safe to thetouch. Likewise, cutting meat with a hemostasis setting would slightlysear the exterior of the meat, locking in juices. Other uses of theinstruments discussed herein will be understood by those skilled in theart in light of the present description.

There is thus disclosed an improved thermally adjustable surgicalinstrument. It will be appreciated that numerous changes may be made tothe present invention without departing from the scope of the claims.

1. A thermal resecting instrument comprising: a thermal elementcomprising: a conductor loop defining a void for receiving tissue and aferromagnetic layer covering at least a portion of the conductor loop,the ferromagnetic layer forming a ferromagnetic region disposed alongthe conductor loop, the conductor loop extending from a position priorto the ferromagnetic layer, through the ferromagnetic region and to aposition beyond the ferromagnetic layer; wherein passage of electricalenergy from a conductor loop location prior to the ferromagnetic regionto a conductor loop location beyond the ferromagnetic region causes theferromagnetic layer to heat.
 2. The thermal resecting instrument ofclaim 1, wherein the ferromagnetic region extends along the conductorloop so as to form a generally semi-circular ferromagnetic region. 3.The thermal resecting instrument of claim 1, wherein the ferromagneticregion extends along substantially the entire length of the conductorloop.
 4. The thermal resecting instrument of claim 1, wherein theconductor loop comprises a material having a Young' Modulus of at least118 GPa.
 5. The thermal resecting instrument of claim 1, wherein theconductor loop comprises a material having a Young's Modulus of at leastabout 400 GPa.
 6. The thermal resecting instrument of claim 1, whereinthe conductor loop further comprises a support extending substantiallythe full length of the conductor loop.
 7. The thermal resectinginstrument of claim 6, wherein the conductor loop further comprises atleast one intervening layer disposed between the support and theferromagnetic layer.
 8. The thermal resecting instrument of claim 1,further comprising a body, wherein the thermal element is connected tothe body and disposed at angle such that the thermal element is orientedin a non-parallel position with respect to the body.
 9. A method oftreating tissue comprising: selecting a surgical tip having a continuousconductor having a first end and a second end and a ferromagneticmaterial disposed along an elongate section of the continuous conductorto form a ferromagnetic region between the first end and the second end;providing oscillating electrical energy to the first end or the secondend of the continuous conductor such that passage of electrical energyfrom a conductor location prior to the ferromagnetic region to aconductor location beyond the ferromagnetic region causes theferromagnetic material to heat; and contacting tissue with the heatedferromagnetic region to thereby treat the tissue.
 10. The methodaccording to claim 9, wherein the continuous conductor forms a loopdefining a void, wherein the method further comprises surrounding tissuesuch that the tissue is located within the void and drawing the heatedferromagnetic region through the tissue to resect the tissue and therebyleave a three dimensional void.
 11. The method according to claim 9,further comprising contacting tissue with an outer surface of the heatedferromagnetic region to incise tissue.
 12. The method according to claim10, further comprising resecting the tissue in one continuous motion.13. The method according to claim 9, wherein the continuous conductorcomprises a material having a Young' Modulus of about 400 GPa so thatthe continuous conductor resists bending when used to treat tissue. 14.The method according to claim 9, wherein the continuous conductorcomprises tungsten.
 15. The method according to claim 9, wherein thecontinuous conductor has at least one intervening layer disposed betweenthe continuous conductor and the ferromagnetic material.
 16. The methodaccording to claim 9, wherein the ferromagnetic material is disposedcircumferentially around the conductor.
 17. The method according to 9,wherein contacting tissue with the heated ferromagnetic region to treatthe tissue includes simultaneously resecting tissue while causinghemostasis.
 18. A thermal resecting system comprising: a handpiece,further comprising: a continuous conductor having a first end and asecond end and defining a void through which tissue can pass; aferromagnetic layer covering at least a portion of the continuousconductor between the first end and the second end; and electrical leadsattached to the first end and the second end of the continuous conductorfor supplying electrical energy to the continuous conductor; a powersupply in communication with the electrical leads for providingelectrical energy to the continuous conductor.
 19. The thermal resectingsystem of claim 18, wherein passage of electrical energy at apredetermined frequency through the continuous conductor and theferromagnetic layer causes direct heating of the ferromagnetic layersufficient to treat tissue.
 20. The thermal resecting system of claim19, wherein the continuous conductor has a generally loop-shaped portionand wherein the ferromagnetic layer covers about half of the loop-shapedportion.
 21. The thermal resecting system claim 19, wherein thecontinuous conductor has a generally loop-shaped portion and wherein theferromagnetic layer covers substantially the entire loop-shaped portion.22. The thermal resecting system of claim 19, wherein heating of theferromagnetic layer is substantially uniform.